JPH11160187A - Leakage detecting method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a leakage detecting method capable of making high- accuracy detection and having less effect of the environment regardless of the material of a buried pipe in the survey of the leakage position of the buried pipe. SOLUTION: The gas in the detection zone of a water service pipe 1 is sucked by a vacuum pump 6 to decompress the air pressure below the atmospheric pressure, preferably to -0.01 MPa or below, air flows into the pipe 1 from a leakage section, and a leakage sound is generated by an air current vortex in the pipe 1 and the collision of an air current with a pipe inner wall. The leakage sound propagated in the pipe 1 and on the pipe wall is detected by detectors 8, 9 and converted into electric signals, and the electric signals are amplified by leakage detector child machines 12, 13 and transmitted to a leakage detector parent machine 14. The transmitted signals are analyzed to calculate the time difference until the leakage sound reaches the detectors 8, 9 from the leakage position, and the distances from the detectors 8, 9 to the leakage position is calculated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a leak detecting method for detecting a leak position in a buried conduit through which a fluid such as a water pipe or a gas pipe flows.

[0002]

2. Description of the Related Art Conventionally, as a method of detecting leakage of a buried pipeline,
Audible sound leak detection methods are known. This method is illustrated in FIG.
As shown in the figure, the leak sound that occurs at the leak point of a buried pipeline such as a water pipe, propagates in the ground and reaches the ground surface is detected on the ground with a detector such as an acceleration sensor, and this is worked with an amplifier. This is a method in which the sound is amplified to such an extent that a person can hear the sound, and the leaked part is detected based on the loudness of the leaked sound or its change.

However, in this method, since the leaked sound is attenuated before it propagates through the ground and reaches the ground surface, it is necessary to be skilled in distinguishing the leaked sound from the noise. Had problems such as being difficult to detect.
For this reason, recently, a correlation type leak detection method is often used.

In the correlation type leak detection method, as shown in FIG. 8, leak sound detectors 51, 51 are disposed at two appropriate places (for example, a valve and a meter) in a buried pipeline, and naturally generated at the leak location. Each of the leak sound detectors 51 detects a leak sound which is generated or a leak sound which is forcibly generated by pumping gas or liquid into a buried pipeline.
, The detected leaked sound signal is amplified by each of the leak detector subunits 52 and 52, and the amplified signal is transmitted to the leak detector main unit 53 disposed on the ground. In this method, the time difference between the transmission signals is calculated, and the distance from the leak location to the leak sound detectors 51, 51 is measured.

[0005]

However, in such a conventional correlation type leak detection method, sound waves propagating in the buried pipe itself are detected by leak sound detectors 51, 51 installed in a valve or a meter. Therefore, although there is less influence than the above-mentioned acoustic detection method, the detection accuracy is not only lowered because the surrounding noise is mixed, but also in the case of a buried pipe with low sound wave propagation, detection of sound waves becomes difficult, and detection is difficult. There was also the problem that it became impossible.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned conventional problems, and has less influence of the environment on detection accuracy, and is capable of performing highly accurate detection regardless of the material of the buried pipe. No detection method is provided.

[0007]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, a leak detection method according to the present invention reduces the pressure of at least the detection section of a buried pipeline to a pressure lower than atmospheric pressure, preferably -0.01 MPa or less, and reduces the pressure from a leak portion. Air leaks into the pipe, and a leak point is detected by detecting a sound wave generated when the air flows and transmitted through the pipe or inside the pipe wall.

In the method of the present invention, as shown in FIG. 5, the air flowing into the pipe from the leaking portion, which is a small hole or a crack, forms an airflow vortex in the pipe. Also produces a leak sound due to collision with the inner wall of the pipe. The sound wave thus generated and transmitted through the inside of the pipe or the pipe wall is detected by a detector, and the leak data is detected by analyzing the detection data. On the other hand, in the conventional correlation type leak detection method, FIG.
As shown in (1), gas or liquid flows out of the pipe from the leaking part, and the gas or liquid flow generated by the outflow collides with foreign matter such as earth and sand outside the pipe to generate a sound wave. Then, the sound wave generated and transmitted through the pipe wall is detected by a detector, and the detection data is analyzed to detect a leaked portion.
Therefore, according to the present invention, compared with the conventional correlation type leak detection method, it is possible to remarkably suppress the deterioration of the detection accuracy due to the influence of the environment such as ambient noise and the influence of the material of the buried pipe, so that a small leak Even if it is a sound, it is possible to reliably detect the position of the leakage point.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings.

FIG. 1 is a diagram showing piping of a water pipe to which the leak detection method of the present invention is applied, and FIG. 2 is a diagram showing an example of an apparatus according to an embodiment of the present invention. In this figure, a section 1A-1B is a leak detection section. The present invention can be applied not only to the detection of a leak in a buried pipeline for sending gas such as city gas, but also for a buried pipeline for sending a liquid such as a water pipe. Moreover, the present invention can be applied regardless of the material, diameter, wall thickness, and burial depth of the pipe.

First, the configuration of the apparatus shown in FIG. 2 will be described. After draining water between the meter 2 and the faucet 3 located at both ends of the section including the detection section 1A-1B, the meter 2 in the meter box is removed. And a mounting jig 4 having a connecting port 4a and a mounting port 4b is attached to the removed port of the detection section, and the other end of a hose 7 having one end connected to a vacuum pump 6 is connected to the connecting port 4a. And its mounting port 4b
Is attached with the detector 8. Also, the faucet 3 is removed,
A mounting jig 5 having a mounting port 5a is mounted on the removed port on the detection section side, and a detector 9 is mounted on the mounting port 5a. The detectors 8 and 9 are connected to the leak detector subunits 12 and 13 each having a preamplifier via conductors 10 and 11, respectively. These leak detector subunits 12 and 13 are wirelessly connected to the leak detector main unit 14 and Connect with The leak detector base unit 14
By analyzing the signals transmitted from the leak detectors 12 and 13, it is possible to calculate the time difference from when the leaked sound reaches the detectors 8 and 9 from the leak location. Note that the position at which the water pipe 1 is cut off is not limited to the meter 2 and the faucet 3, but may be any two positions on both sides of the section including the section to be detected.
You can shut it off at some point.

As shown in FIG. 3, each of the detectors 8 and 9 is characterized in that a waterproof gas permeable membrane 18 is provided on a vibration detecting surface, and a main body 14, a connector 15 and a lid 1 are provided.
It consists of six. In the main body 14, a waterproof gas-permeable membrane 18 is fixed to one end surface of a hollow cylindrical case 17, one end of the connector 15 is inserted through the other end opening, and the flange of the connector 15 is connected to the other part of the case 17 via packing. By pressing against the end face, the other end opening is sealed.

As shown in FIG. 4, the waterproof gas permeable membrane 18 is made of a porous membrane having a selective permeability that does not allow gas to pass through a liquid, such as Gore-Tex (registered trademark), on a support material layer 18a made of a polyester nonwoven fabric. Waterproof breathable material layer 18
b, and an adhesive layer 18c is formed on the periphery of the waterproof breathable material layer 18b.
a, an adhesive material layer 18c, and a waterproof gas-permeable material layer 18b to form a three-layer structure, and a support material layer 18a and a waterproof gas-permeable material layer 1
At the interface between 8b, liquids such as water, sulfuric acid and nitric acid cannot pass, but gas such as air and water vapor can pass.

A microphone 20 is disposed at one end of the case 17 by a holding member 19 made of an elastic member, and a microphone 20 is disposed near a detection surface thereof near the waterproof gas-permeable membrane 18.
Each lead wire of the microphone 20 is connected to each terminal pin of the connector 15, and the connection portion is coated with epoxy resin for sealing. The microphone 20 is of a unidirectional condenser type having directivity in the passing direction in order to detect a leaked sound that has passed through the waterproof gas-permeable membrane 18. As a result, there is no difference between the air pressures P ₁ and P ₂ before and after the detection direction of the microphone 20, and stable measurement accuracy can be ensured.

According to the detectors 8 and 9 having such a configuration, at the interface of the waterproof gas-permeable material layer 18b, moisture and other liquids cannot pass, only gas can pass, and the sound pressure of the water leakage sound can be reliably reduced. Can be detected, and the waterproof breathable membrane 1
Since the microphone 19 of the unidirectional condenser type is arranged close to 8, the sound pressure of the water leakage sound can be detected with high accuracy.

The procedure for executing the detection method will be described below.

The vacuum pump 6 is operated to suck the gas in the water pipe 1 to reduce the pressure to less than atmospheric pressure, preferably -0.0
Adjust to 1 MPa or less. After adjusting the atmospheric pressure to a desired range, the operation of the vacuum pump 6 is temporarily stopped. As a result, the operation sound of the vacuum pump 6 and the pulsation of the gas in the water pipe 1 are eliminated, and only the leakage sound can be detected.

Since the pressure inside the water pipe 1 is lower than the pressure outside the pipe, as shown in FIG. 5, the air that has flowed into the pipe from the leak portion becomes an air vortex in the pipe, and this air vortex generates a leak sound. At the same time, the air flowing into the pipe from the leak part collides with the pipe inner wall, and this collision also generates a leak sound,
These leak sounds propagate through the inside of the pipe or the pipe wall, and the detectors 8 and 9
To reach. The sound waves detected by the detectors 8 and 9 are converted into electric signals, amplified by the leak detectors 12 and 13, and transmitted to the leak detector master unit 14. The leak detector main unit 14 analyzes this transmission signal, calculates the time difference between the leak location and the leak sound reaching the detectors 8 and 9, and calculates the distance from the detectors 8 and 9 to the leak location.

[Detection Test of Leak Point] The leak of water pipes was actually detected by various methods, and the effects of the present invention were examined by comparing the measurement results.

In this test, the water pipe to be detected is made of hard vinyl chloride, having a diameter of 20 mm and a wall thickness of 2.
Connect 7 mm water pipes as appropriate, and place 0.5 m
A perforated hole having a diameter of m was used.

In tests 1 to 4, a detector (a sound wave detector with a waterproof gas-permeable membrane, manufactured by Fujitecom Co., Ltd.) was placed at a distance of 4.23 m and 3.43 m on both sides from the position where the leak hole of the water pipe was formed. Portacol LC-2100 sensor)
8 and 9 were installed, and in accordance with the above-described procedure of the detection method of the present invention, the water pressure in the water pipe was changed by using a pump (a compression pump in tests 1 and 2 and a vacuum pump in tests 3 and 4) as shown in Table 1. Was adjusted. Then, the sound waves propagating in the pipe are detected by the detectors 8 and 9 and converted into electric signals, and the sound waves are detected by the leak detector subunit 12 (“Portacol” L manufactured by Fujitecom Co., Ltd.).
Amplified by the C-2100 preamplifier and leak detector parent device 14 ("Portacol" LC, manufactured by Fujitecom)
9 to 12), and the analysis waveforms of the obtained leaked sound data are shown in FIGS. In each figure (similarly in FIG. 13), the vertical axis represents the degree of correlation, and the horizontal axis represents T.
d (delay time), and “LEAK B” indicates the distance from one detector 8 (color BRUE) to “LEAK B”.
“AKR” is the distance from the other detector 9 (color is RED), and “F” is the set value of the filter (for example, high range 2500).
Hz, low frequency 180 Hz), "Td" indicates that the delay time of the peak (for example, Td 1.3 ms) indicates that the position of the peak (leakage point) is 1.3 ms closer to the red detector side than the center. ), “SUM” indicates the number of samples, and “YZ” indicates a display multiple of the degree of correlation (for example, YZ3 triples the correlation waveform on the vertical axis).

In test 5, the conventional correlation type leak detection method,
That is, as shown in FIG. 8, leak sound detectors 51 and 51 (piezoelectric acceleration sensors manufactured by Fujitecom, voltage sensitivity 5 V / g (600 Hz)), water is fed into the water pipe at a pressure of 0.3 MPa to 0.4 MPa, and a leak sound propagating through the pipe wall is detected by a leak sound detector 51,
The leak sound signal detected by the detector 51 is detected by the leak detector subunits 52, 52 ("Portacol" LC-2 manufactured by Fujitecom Inc.).
100 preamplifiers), and the leakage detector parent device 53
(The main body of "Portacol" LC-2100, manufactured by Fujitecom), and the received signal is converted into a waveform as shown in FIG.
3 is shown.

Based on the above results, whether or not a correlation result was obtained in each test is summarized in Table 1 below. In addition,
Whether the correlation result was obtained or not was determined based on whether or not the peak of the leak point appeared in each of FIGS. 9 to 13.

[0024]

[Table 1]

As a result, when water is fed into the pipeline,
And when the air was pumped at 0.4 MPa or more, no correlation results could be obtained. That is, the position of the leak hole could not be determined. On the other hand, when the air was pumped at 0.1 MPa or less, or when the pressure was reduced by sucking the air, the correlation result was obtained, and the position of the leak hole could be obtained. However, when air is pumped at a pressure of 0.1 MPa or less, the peak value is low, that is, the measurable intensity is low, as can be seen from the fact that the intensity (correlation degree) on the vertical axis is tripled and displayed in FIG. Because it is weak, it is expected that detection will become impossible if the detection length is long. For this reason, it is considered preferable to detect the leakage point of the buried pipe by suctioning air in the detection section and reducing the pressure to below the atmospheric pressure.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing an arrangement of a water pipe to which a leak detection method of the present invention is applied.

FIG. 2 is a cross-sectional view illustrating an example of an embodiment of a leak detection method according to the present invention.

FIG. 3 is a sectional view showing an example of the detector of FIG.

FIG. 4 is a sectional view of a waterproof gas-permeable membrane.

FIG. 5 is a cross-sectional view illustrating the flow of air in a leak portion when the pressure in the pipe is reduced.

FIG. 6 is a cross-sectional view illustrating the flow of air in a leak portion when the inside of a pipe is pressurized.

FIG. 7 is a cross-sectional view illustrating a conventional sound-based leak detection method.

FIG. 8 is a cross-sectional view illustrating a conventional correlation type leak detection method.

FIG. 9 is an analysis waveform of leak sound data when the pressure in the pipe is adjusted to 0.3 MPa to 0.4 MPa.

FIG. 10 is an analysis waveform of leak sound data when the pressure in the pipe is adjusted to 0.06 MPa to 0.1 MPa.

FIG. 11 is an analysis waveform of leak sound data when the pressure in the pipe is adjusted to −0.05 MPa.

FIG. 12 is an analysis waveform of leak sound data when the pressure in the pipe is adjusted to −0.01 MPa.

FIG. 13: Water is supplied into the pipe, and the water pressure in the pipe is 0.3 MPa to
It is the graph which showed the sound wave which the detector detected when it adjusted to 0.4MPa as a waveform.

[Explanation of symbols]

 Reference Signs List 1 water pipe 2 meter 3 faucet 4,5 mounting jig 6 vacuum pump 7 hose 8,9 detector 10 conductor 12,13

Claims (2)

[Claims] At least a detection section of a buried pipeline is depressurized to a pressure lower than the atmospheric pressure, air flows into the pipe from a leak portion, and a sound wave generated when the air flows in and transmitted through the pipe or the pipe wall is generated. A leak detection method characterized by detecting a leak location by detecting. 2. The leak detection method according to claim 1, wherein the pressure in the detection section is reduced to −0.01 MPa or less.